Thioheteropoly acid anhydrides as crude oil hydrorefining catalysts



United States Patent ABSTRACT OF THE DISCLOSURE A catalyst for the hydrorefining of petroleum crude oil comprising the anhydride of a thioheteropoly acid having the formula in which n is 12, 18 or 24; X is Mo, W, Cr or V; and m is 1 when X is M0 or W, or 2 when X is Cr or V.

The invention described is adaptable to a process for the hydrorefining of heavy hydrocarbon fractions and/ or distillates. More specifically, the present invention is directed toward a novel catalytic composite for particular utilization in treating petroleum crude oils and topped, or reduced crude oils for the primary purpose of removing organo-metallic contaminants, while simultaneously converting pentane-insoluble asphaltenic material into soluble, normally liquid hydrocarbons.

Petroleum crude oils, and topped or reduced crude oils, as well as other heavy hydrocarbon fractions and/ or distillates, including black oils, heavy cycle stocks, visbreaker liquid etrluent, crude tower bottoms product, tar sand oils, etc., are contaminated by the inclusion of excessive quantities of various non-metallic and metallic impurities which detrimentally affect various processes in which such heavy hydrocarbon mixtures may be employed. Among the non-metallic impurities are nitrogen, sulfur and oxygen which exist as heteroatomic compounds, nitrogen probably being most undesirable because it effectively poisons catalytic composites which may be employed in various processes for the conversion of petroleum fractions. Both nitrogenous and sulfurous compounds are objectionable since combustion of fuels containing these impurities results in the release of nitrous and sulfur oxides which are noxious, corrosive, and present, therefore, a serious problem with respect to pollution of the atmosphere. In regard to motor fuels, sulfur and sulfurous compounds are particularly objectionable because of odor, gum and varnish formation, and significantly decreased lead susceptibility. In addition to the foregoing described contaminating influences, petroleum crude oils and other heavy hydrocarbonaceous material, contain high molecular weight asphaltenic compounds. These are non-distillable, oil-insoluble coke precursors which often are found to contain sulfur, nitrogen, oxygen and various metals. Of the metallic contaminants, those containing nickel and vanadium are most common although other metals including iron, copper, lead, zinc, etc., are often present in significantly detrimental quantities. Although the metallic contaminants may exist within the hydrocarbonaceous material in a variety of forms, they are generally found as organo-metallic compounds of relatively high molecular weight, including metallic porphyrins and the various derivatives thereof. A significant quantity of the organo-metallic complexes are linked with asphaltenic material and become concentrated in the residual fraction; other organo-metallic complexes are volatile, oil-soluble, and are, therefore, present in the lighter distillate fraction. A reduction in the concentration of the organo-metallic complexes is not easily achieved, and to the extent that the crude oil, reduced crude oil, or other heavy hydrocarbon charge stock derived therefrom, becomes suitable for further processing. Notwithstanding that the concentration of these organometallic complexes may be relatively small, in a lighter distillate fraction often less than about 10 p.p.m., calcu lated as if the complex existed as the elemental metal, subsequent processing techniques are adversely affected thereby. With respect to a process for hydrorefining or treating of hydrocarbon fractions 01' distillates, the presence of large quantities of asphaltenic material and organo-metallic compounds interferes considerably with the activity of the catalyst to effect the destructive removal of the nitrogenous, sulfurous and oxygenated compounds, which function is normally the easiest for the catalytic composite to perform to an acceptable degree. Therefore, it is highly desirable to produce a hydrocarbon mixture substantially free from asphaltenic material and organo-metallic compounds, and which is substantially reduced in nitrogen and sulfur concentration.

A wide variety of heavy hydrocanbon fractions and/or distillates may be treated, or decontaminated effectively through the utilization of the catalytic composite of the present invention. Such heavy hydrocarbon fractions include full boiling range crude oils, topped or reduced crude oils, atmospheric distillates, visbreaker bottoms product, heavy cycle stocks from thermally or catalytically-cracked charge stocks, heavy vacuum gas oils, tar sand oils, etc. Such heavy hydrocarbonaceous material includes a Wyoming sour crude oil, having a gravity of 232 API at 60 F., and contaminated by the presence of about 2.8% by weight of sulfur, 2700' p.p.m. of total tnitrogen, approximately 100 p.p.m. of metallic complexes, computed as the elemental metals, and comprising a high boiling, pentane-insoluble asphaltenic fraction in an amount of about 8.4% by weight. A more difficult charge stock to convert into useful liquid hydrocarbons, is a crude tower bottoms product having a gravity API at 60 F., of 14.3, and contaminated by the presence of 3.0% by weight of sulfur, 3,830 p.p.m. of total nitrogen, p.p.m. of total metals and about 10.93% by weight of asphaltenic compounds. Similarly, an atmospheric tower bottoms product, having a gravity of 7.0 API at 60 F., is contaminated by 6,060 p.p.m. of total nitrogen, 4.05% by weight of sulfur, more than 450 p.p.m. of total metals, and contains an asphaltenic fraction in an amount of 24.0% by weight.

The object of the present invention is to provide a catalytic composite suitable for use in a process for hydrorefining heavy hydrocarbonaceous material, and particularly full boiling range crude oils, and topped or reduced crude oils. The use of the catalyst of the present invention affords the utilization of either a fixed-bed, or fixed-fluidized hydrorefining process, or a slurry-type process in which the catalytic composite and charge stock are intimately admixed. Heretofore, the fixed-bed hydrorefining process has not been considered feasible due to the deposition of coke and other gummy carbonaceous material within the reaction zone. Although the difficulties encountered in a fixed-bed catalytic process are at least par tially solved by a moving-bed or slurry-type operation, wherein the finely-divided catalytic composite is intimately admixed with the hydrocarbon charge stock, the mixture being subjected to the desired operating conditions, there exists the disadvantage of having a relatively small amount of catalyst being admixed with relatively large quantities of asphaltenic material. In other words, two few catalytically active sites are made available for immediate reaction, with the result that the asphaltenic material has the tendency to undergo thermal cracking,

resulting in the production of large quantities of light gases and coke. The difficulties are in turn partially avoided through the utilization of a fixed-fluidized process in which the catalytic composite is disposed within a confined reaction zone, being maintained, however, in a fluidized state by exceedingly large quantities of a fastfiowing hydrogen-containing gas stream.

The crude oil hydrorefining catalyst of the present invention permits effecting the process in a fixed-bed unit without incurring the difficulties hereinbefore described. Furthermore, the catalyst, when unsupported, permits an efiicient utilization of a slurry-type process. When combinded with a suitable refractory inorganic oxid carrier material, the catalyst hereinafter described also permits the economic utilization of the fixed-fluidized bed process. In any event, the catalyst of the present invention is especially advantageous in effecting the removal of organometallic compounds while simultaneously converting pentane-insoluble material into pentane-soluble liquid hydrocarbons, and effecting the destructive removal of significantly large quantities of sulf-urous and nitrogenous com pounds.

In a broad embodiment, the present invention relates to a hydrorefining catalyst which comprises the anhydride of a thioheteropoly acid consisting of thiophosphoric acid acid in combination with at least one thio acid selected from the group consisting of vanadium and the metals of Group VI-B of the Periodic Table.

A more limited embodiment of the present invention encompasses a hydrorefining catalyst which comprises the anhydride of a thioheteropoly acid consisting of thiophosphoric acid in combination with at least one thio acid selected from the group consisting of vanadium and the metals of Group VI-B, the mol ratio of said thio acid to phosphorus being a multiple of three within the range of 6:1 to 12:1.

As hereinbefore set forth, the catalyst may be combined with a suitable carrier material for utilization in a fixed-bed process for the hydrorefining of petroleum crude oils. Therefore, the present invention also involves a hydrorefining catalyst comprising a composite of silica and from about 12.0% to about 88.0% by weight of alumina, combined with from about .0% to about 30.0% by weight of the anhydride of thioheteropoly acid consisting of thiophosphoric acid in combination with at least one thio acid selected from the group consisting of vanadium and the metals of Group VI-B of the Periodic Table.

The hydrorefining process, for which the catalyst of the present invention is particularly adaptable, is effected by reacting the hydrocarbon charge stock, such as a petroleum crude oil containing pentane-insoluble asphalenes, with hydrogen, in the presence of from about 1.0% to about 15.0% by weight of hydrogen sulfide, and in contact with the catalyst at a temperature within the range of from about 225 C. to about 500 C. and under a pressure about 500 p.s.i.g., having an upper limit of 5,000 p.s.i.g'.

From the foregoing embodiments, it is noted that the present invention involves a catalyst utilizing phosphorus, vanadium and metals selected from Group VI-B of the Periodic Table. Reference is herein made to the Periodic Chart of the 'Elements, pages 448 and 449, 43rd edition of Handbook of Chemistry and Physics. It will be further noted from the foregoing embodiments that the catalyst of the present invention is selected from anhydrous thioheteropoly acids comprising particular combinations of the thio acids of the aforesaid metals. In general, it may be stated that a thioheteropoly acid is a combination of thio-metallic acids selected from Group VI-B of the Periodic Table, and thiophosphoric acid Thus, the anhydrous thioheteropoly acid will comprise a combination of at least one thio acid selected from the group consisting of thiomolybdic acid, thiotungstic acid, thiochromic acid and thiovanadic acid with thiophosphoric acid.

The anyhydride of the thioheteropoly acid of the present invention will have the following formula:

wherein, n is a multiple of three, and selected from 12, 18 and 24, such that the mol ratio of X to phosphorus is a multiple of three within the range of from 6 to 12; and X designates Mo and W in the case of molybdenum and tungsten, and Cr and V in the case of chromium and vanadium.

Exemplary of the anhydrides of the thioheteropoly acids consisting of combinations of the foregoing thio acids include the anhydrides of thiomolybdic acid-thiophosphoric acid, thiotungstic acid-thiophosphoric acid, thiovanadic acid-thiophosphoric acid and thiochromic acid-thiophosphoric acid. Particularly preferred anhydrides are the following:

In many instances the anhydrous thioheteropoly acid will consist of a combination of three of the foregoing described thio acids. Such thioheteropoly acid are exemplified by thiomolybdic acid-thiophosphoric acid-thiovanadic acid, thiomolybdic acid-thiotungstic acid-thiophosphoric acid, and thiotungstic acid-thiophosphoric acid-thiochromic acid. The anhydrides particularly preferred as hydrorefining catalysts are those of the thioheteropoly acids which are combinations of either and/ or both thiomolybdic acid and thiotungstic acid with thiophosphoric acid.

When intended for utilization in a slurry-type process, the catalyst, for example the anhydride of the thioheteropoly acid formed by a combination of thiophosphoric acid with 12 mols of thiotungstic acid, represented by the formula, P S '12WS is admixed with the charge stock in an amount of from about 5.0% to about 30.0% by weight thereof. In order to facilitate the formation of the colloidal suspension, or dispersion of the anhydride within the charge stock, the desired quantity of tungsten sulfide (WS is dissolved in molten phosphorus sulfide (P S at a temperature below its boiling point, and preferably within the range of from about 300 C. to about 400 C. Any excessive quantity of phosphorus sulfide can be removed at a temperature of about 300 C. under a vacuum, the remaining solid being powdered and added to the crude oil.

When effected as a slurry-type process, the hydrorefining of petroleum crude oils, utilizing the catalyst of the present invention, may be conducted in a batchtype manner or in an enclosed vessel through which the colloidal suspension is passed; when carried out in a continuous manner, the process may be conducted in either upward flow or downward flow. The normally liquid hydrocarbons are separated from the total reaction Zone effluent by any suitable means, for example, through the use of a centrifuge or series of settling tanks, at least a portion of the remaining catalyst-containing sludge being combined with the fresh petroleum crude oil and recycled to the reaction zone. In order to maintain the highest possible degree of activity, it is preferred that at least a portion of the catalyst-containing sludge be removed from the process prior to combining the remainder with fresh crude oil. The precise quantity of catalyst-containing sludge removed from the process will be dependent upon the desired degree of contaminant removal. It is further desirable to add a quanity of the thioheteropoly acid anhydride to the petroleum crude oil in order to compensate for that quantity removed with the catalyst-containing sludge, such that the catalyst concentration is within the range of from about 5.0% to about 30.0% by weight of the total mixture within the reaction zone.

When intended for use in a fixed-bed, or fixed-fluidized process, the thioheteropoly acid anhydride, for example, P S -18MoS is combined with a suitable refractory organic oxide carrier material. Although the precise composition and method of manufacturing the carrier material is not considered a limiting feature of the present invention, the preferred carrier material, in order to have the most advantageous physical and chemical structure, will contain at least a portion of alumina and have an apparent bulk density less than about 0.35 grams/cc. The preferred catalytic composite comprises a carner material of silica and from about 12.0% to about 88.0% by weight of alumina. In many instances, however, other refractory inorganic oxides may be advantageously employed in conjunction with the alumina, and include zirconia, magnesia, titania, boria, strontia, hafma, boron phosphate and mixtures of two or more. By way of specific examples, a satisfactory carrier material may comprise equimolar quantities of alumina and silica, or 63.0% by weight of alumina and 37.0% by weight of silica, or a carrier of 68.0% by weight of alumina, 10.0% by weight of silica and 22.0% by weight of boron phosphate. The carrier material may be formed by any of the numerous techniques which are rather well defined in the prior art. Such techniques include the acid-treating of a natural clay, sand or earth, co-precipitation, or successive precipitation from hydrosols, which techniques are frequently coupled with one or more activating treatments including hot oil aging, steaming, drying, oxidizing, reducing, calcining, etc. The pore structure of the carrier material, commonly defined in terms of surface area, pore diameter and pore volume, may be developed to specified limits by any means including aging the hydrosol and/ or hydrogel under controlled acidic or basic conditions, or by gelling the carrier at a critical pH, or by treating the carrier with various inorganic or organic reagents.

The hydrorefining catalytic composite is prepared by initially forming an alumina-containing refractory inorganic oxide carrier material having the foregoing described characteristics. For example, an alumina-silica composite containing about 63.0% by weight of alumina is prepared by the co-precipitation of the respective hydrosols. The precipitated material, generally in the form of a hydrogel, is dried at a temperature of about 100 C. and for a time sufiiciently long to remove substantially all of the physically-held water. The composite is then subjected to a high-temperature calcination technique, in an atmosphere of air, for a period of about one hour at a temperature above about 300 C., which technique serves to remove the greater proportion of the chemicallybound water. The calcined carrier material is then combined with the thioheteropoly acid anhydride, preferably by way of an impregnating technique utilizing a solution of molybdenum sulfide in molten phosphorus sulfide. The thioheteropoly acid anhydride, or mixture thereof, is utilized in an amount such that the final catalytic composite comprises from about 5.0% to about 30.0% by weight. The impregnated alumina-containing composite is calcined at a temperature within the range of about 550 C. to about 60 C., in a suitable inert atmosphere, to remove any excessive phosphorus sulfide.

The fixed-bed hydrorefining process, utilizing the catalyst prepared in accordance with the method of the present invention, may be effected by initially admixing the hydrocarbon charge stock with hydrogen in an amount within the range of from about 5,000 to about 50,000 s.c.f./bbl. of liquid hydrocarbons. The mixture is heated to a temperature of from about 225 C. to about 500 C., and passes into the reaction zone maintained under an imposed pressure within the range of about 500 to about 5,000 pounds per square inch. The hydrocarbon charge stock contacts the fixed-bed of catalyst at a liquid hourly space velocity, (defined as volumes of liquid bydrocarbon charge per hour per volume of catalyst disposed within the reaction zone), of from about 0.5 to

about 5.0. It is preferred that the reaction zone atmosphere comprise hydrogen sulfide which has been added with the hydrogen-containing gas stream as distinguished from that which may be produced via the hydrogenation/ hydrocracking reactions. That is, the beneficial effects of added hydrogen sulfide appear to occur only when the latter is present at the time the hydrogenation reactions are being initiated. The hydrogen sulfide is added to the hydrogen atmosphere in an amount of from about 1.0 to about 15.0 mol percent. The precise operating conditions, including temperature and pressure, are at least partially dependent upon the physical and chemical characteristics of the hydrocarbon charge stock, the length of the period during which the catalyst has been functioning, and the desired end result. It is understood that the operating conditions, under which the catalytic composite of the present invention is employed, are not limiting upon the scope of the appended claims. The following examples are given for the purpose of illustrating the method by which the catalyst of the present invention is prepared, and the benefits afforded the hydrorefining of heavy hydrocarbonaceous material through the utilization thereof. The charge stocks, temperatures, pressures, catalysts, rates, etc., are herein presented as being exemplary only, and are not intended to limit the present invention to an extent greater than that defined by the scope and spirit of the appended claims.

EXAMPLE I The charge stock employed in illustrating the fixedbed hydrorefining process, utilizing the catalyst of the present invention, is a topped Wyoming sour crude oil. The topped crude indicates a gravity, API at 60 F., of 19.5, and contains 3.0% by weight of sulfur, about 2,900 p.p.m. of total nitrogen, ppm. of nickel and vanadium, the pentane-insoluble asphaltenic fraction being about 8.5% by weight.

The catalytic composite is a spray-dried alumina-silica carrier material containing about 63.0% by weight of alumina on a dried basis. The spray-dried composite is oxidized or calcined in an atmosphere of air for a period of about one hour at a temperature of about 550 C. An impregnating solution is prepared utilizing a molten phosphorus sulfide solution of molybdenum sulfide at a temperature of 350 C., and in an amount to produce a final catalyst comprising about 15.0% by weight of the thioheteropoly acid anhydride. The alumina-silica carrier material is impregnated with the solution, and calcined at a temperature of about 575 C. for a period of about two hours in an atmosphere of nitrogen. The final com posite, having a particle size ranging from about 20 to about microns, is disposed as a fixed-bed in a reaction zone in an amount of about 200 grams. The temperature of the catalyst is increased to a level of about 400 C., and hydrogen circulation through the catalyst is begun. Hydrogen is admixed with the previously described topped Wyoming sour crude oil, in an amount of about 25,000 s.c.f./bbl. of liquid charge, a compressor being utilized to maintain the pressure Within the reaction zone at aobut 1,500 pounds per square inch.

The reaction products from the reaction zone are continuously cooled and passed into a high-pressure separator from which a liquid hydrocarbon product is removed to a receiver, the hydrogen-rich gas stream being removed through a Water scrubber and recycled to the reaction. In order to compensate for that quantity of hydrogen consumed Within the process, and absorbed in the normally liquid hydrocarbon eflluent, fresh hydrogen is added to the recycle gas stream as determined by the operating pressure within the reaction zone, and this instance being an amount of about 2,000 s.c.f./bbl. For approximately one-half of its effective, acceptable life, the catalytic composite will promote the hydrogenation/hydrocracking reactions required to produce a normally liquid product substantially free from pentane-insoluble asphaltenes, organo-metallic contaminants and sulfurous and nitrogenous compounds. Thus, the normally liquid product effluent will contain less than about 0.5% by weight of pentane-insoluble asphaltenic material, less than about 0.5 p.p.m. of organo-metallic compounds, less than 50 p.p.m. of total nitrogen and less than about 0.10% by weight of sulfur, the gravity thereof, API at 60 F., being within the range of about 30.0 to 32.0.

As hereinbefore set forth, the presence of excessive quantities of pentaneinsoluble asphaltenes as well as the organo-metallic compounds, interferes considerably with the capability of the catalyst to effect the destructive removal of nitrogenous and sulfurous compounds. Therefore, the catalyst will indicate a normal activity decline through an increase in the concentration of residual sulfurous and nitrogenous compounds in the normally liquid product efrluent. However, since the pentaneinsoluble asphaltenes and organo-metallic compounds will be below the previously determined range of 0.5% by weight and 0.5 p.p.m. respectively, the operation may be continued on an economic basis notwithstanding a comparatively high concentration of residual nitrogenous and sulfurous compounds. In this situation, the normally liquid product efiiuent is subjected to a second stage operation at significantly more severe conditions for the purposes of effecting the complete destructive removal of the remaining sulfurous and nitrogenous compounds.

EXAMPLE II The thioheteropoly acid anhydride, P S -18WS in an amount of about 20.0 grams, is added to 200 grams of the Wyoming sour crude oil hereinabove described. The resulting mixture is placed in an 850 cc. rocker-type autoclave, pressured to atmospheres with hydrogen sulfide, then to 100 atmospheres with hydrogen, and slowly heated to a temperature of about 400 0., resulting in a final pressure of about 220 atmospheres; these conditions are maintained for a period of about 8 hours. The autoclave is permitted to cool, and depressured to atmospheric conditions; the normally liquid product effluent indicates a gravity, API at 60 F., of about 32.6. Analyses further indicate that the liquid hydrocarbon fraction is contaminated by only about 150 p.p.m. of nitrogen, 0.20% by weight of sulfur and only about 0.04% by weight of pentane-insoluble asphaltenes. The analyses also show the concentration of organo-metallic porphyrins to be less than about 0.5 p.p.m.

The foregoing specification and examples clearly indicate the benefits afforded a process for hydrorefining petroleum crude oil, and other heavy hydrocarbonaceous material, through the use of the catalyst of the present invention. The contaminating influences have been removed to the extent required for further processing without incurring the deleterious effects otherwise resulting.

I claim as my invention:

1. A hydrorefining catalyst comprising the anhydride of a thioheteropoly acid, said anhydride having the formula:

wherein n is an integer being l2, 18 or 24; X is a metal selected from the group consisting of Mo, W, Cr and V; and m is an integer being 1 when X is M0 or W, or 2 when X is Cr or V.

2. The catalyst of claim 1 further characterized in that X is molybdenum.

3. The catalyst of claim 1 further characterized in that X is tungsten.

4. The catalyst of claim 1 further characterized in that X is chromium.

5. The catalyst of claim 1 further characterized in that X is vanadium.

6. A hydrorefining catalyst comprising from about 5% to about 30% by weight, based on total catalyst, of the anhydride of claim 5 composited with a refractory inorganic oxide carrier consisting essentially of silica and alumina.

References Cited UNITED STATES PATENTS 2,029,100 1/1936 Grosse 208-2l6 2,450,756 10/1948 Hoiberg 252437 X 2,744,928 5/1956 Smith et a1.

OSCAR R. VERTIZ, Primary Examiner.

HERBERT T. CARTER, Assistant Examiner.

US. Cl. X.R. 

